Power equipment with detection and reaction systems

ABSTRACT

Woodworking machines and safety methods for use with those machines are disclosed. The machines include a detection system adapted to detect one or more dangerous conditions and a reaction system associated with the detection system. The reaction system can include an explosive to trigger the system, and also can be configured to retract a cutting tool at least partially away from a cutting region upon detection of a dangerous condition by the detection system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the following U.S. PatentApplications, all of which are hereby incorporated by reference in theirentireties:

Ser. No. 11/796,819, filed Apr. 30, 2007, which is a continuation ofSer. No. 09/929,426, filed Aug. 13, 2001, issuing as U.S. Pat. No.7,210,383 on May 1, 2007, which claims the benefit of and priority froma number of U.S. Provisional Patent Applications including Ser. No.60/225,200, filed Aug. 14, 2000;

Ser. No. 12/655,695, filed Jan. 4, 2010, which is a continuation of Ser.No. 11/975,985, filed Oct. 22, 2007, issuing as U.S. Pat. No. 7,640,835on Jan. 5, 2010, which is a continuation of Ser. No. 09/929,221, filedAug. 13, 2001, issuing as U.S. Pat. No. 7,284,467 on Oct. 23, 2007,which claims the benefit of and priority from a number of U.S.Provisional Patent Applications including Ser. No. 60/225,211, filedAug. 14, 2000;

Ser. No. 12/002,388 filed Dec. 17, 2007, which is a continuation of Ser.No. 09/929,227, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,308,843on Dec. 18, 2007, which claims the benefit of and priority from a numberof U.S. Provisional Patent Applications including Ser. No. 60/225,170,filed Aug. 14, 2000;

Ser. No. 11/401,050, filed Apr. 10, 2006, now U.S. Pat. No. 7,788,999which is a continuation of a number of applications including Ser. No.09/929,240, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,100,483 onSep. 5, 2006, which in turn claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/225,056, filed Aug. 14, 2000;Ser. No. 09/929,241, filed Aug. 13, 2001, issuing as U.S. Pat. No.7,024,975 on Apr. 11, 2006, which in turn claims the benefit of andpriority from a number of U.S. Provisional Patent Applications includingSer. No. 60/225,169, filed Aug. 14, 2000; Ser. No. 09/929,425, filedAug. 13, 2001, issuing as U.S. Pat. No. 7,137,326 on Nov. 21, 2006,which in turn claims the benefit of and priority from U.S. ProvisionalPatent Application Ser. No. 60/225,210, filed Aug. 14, 2000; Ser. No.10/172,553, filed Jun. 13, 2002, issuing as U.S. Pat. No. 7,231,856 onJun. 19, 2007, which in turn claims the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/298,207, filed Jun. 13,2001; Ser. No. 10/189,027, filed Jul. 2, 2002, issuing as U.S. Pat. No.7,712,403 on May 11, 2010, which in turn claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/302,916,filed Jul. 3, 2001; Ser. No. 10/243,042, filed Sep. 13, 2002, issuing asU.S. Pat. No. 7,197,969 on Apr. 3, 2007, which in turn claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/324,729, filed Sep. 24, 2001; Ser. No. 10/643,296, filed Aug. 18,2003, now abandoned, which in turn claims the benefit of and priorityfrom U.S. Provisional Patent Application Ser. No. 60/406,138, filed Aug.27, 2002; and Ser. No. 10/794,161, filed Mar. 4, 2004, issuing as U.S.Pat. No. 7,098,800 on Aug. 29, 2006, which in turn claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/452,159, filed Mar. 5, 2003;

Ser. No. 10/984,643, filed Nov. 8, 2004, which is a continuation of anumber of applications, including Ser. No. 09/929,226, filed Aug. 13,2001, issuing as U.S. Pat. No. 6,920,814 on Jul. 26, 2005, which in turnclaims the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/225,206, filed Aug. 14, 2000; Ser. No.09/929,240, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,100,483 onSep. 5, 2006, which in turn claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/225,056, filed Aug. 14, 2000;Ser. No. 09/929,242, filed Aug. 13, 2001, issuing as U.S. Pat. No.7,509,899 on Mar. 31, 2009, which claims the benefit of and priorityfrom a number of U.S. Provisional Patent Applications including Ser. No.60/225,089, filed Aug. 14, 2000; Ser. No. 10/051,782, filed Jan. 15,2002, issuing as U.S. Pat. No. 6,877,410 on Apr. 12, 2005, which in turnclaims the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/279,313, filed Mar. 27, 2001; Ser. No.10/052,806, filed Jan. 16, 2002, issuing as U.S. Pat. No. 6,880,440 onApr. 19, 2005, which in turn claims the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/270,942, filed Feb. 22,2001; Ser. No. 10/205,164, filed Jul. 25, 2002, issuing as U.S. Pat. No.6,945,149 on Sep. 20, 2005, which in turn claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/307,756,filed Jul. 25, 2001; Ser. No. 10/202,928, filed Jul. 25, 2002, issuingas U.S. Pat. No. 7,000,514 on Feb. 21, 2006, which in turn claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/308,492, filed Jul. 27, 2001; and Ser. No. 10/785,361, filed Feb.23, 2004, issuing as U.S. Pat. No. 6,997,090 on Feb. 14, 2006, which isa continuation of Ser. No. 10/215,929, filed Aug. 9, 2002, nowabandoned, which in turn claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/312,141, filed Aug. 13, 2001;

Ser. No. 11/542,938, filed Oct. 2, 2006, which is a continuation of anumber of applications, including Ser. No. 09/929,242, filed Aug. 13,2001, issuing as U.S. Pat. No. 7,509,899 on Mar. 31, 2009, which claimsthe benefit of and priority from a number of U.S. Provisional PatentApplications including Ser. No. 60/225,089, filed Aug. 14, 2000; Ser.No. 11/401,774, filed Apr. 11, 2006, issuing as U.S. Pat. No. 7,525,055on Apr. 28, 2009, which is a continuation of Ser. No. 11/027,322, filedDec. 31, 2004, now abandoned, which claims the benefit of and priorityfrom U.S. Provisional Patent Application Ser. No. 60/533,598, filed Dec.31, 2003; Ser. No. 11/445,548, filed Jun. 2, 2006, issuing as U.S. Pat.No. 7,347,131 on Mar. 25, 2008; and Ser. No. 11/506,260, filed Aug. 18,2006, issuing as U.S. Pat. No. 7,359,174 on Apr. 15, 2008, which is acontinuation of a number of application including Ser. No. 10/923,282,filed Aug. 20, 2004, now abandoned, which in turn claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,568, filed Aug. 20, 2003;

Ser. No. 12/590,094, filed Nov. 2, 2009, which is a continuation of Ser.No. 09/929,236, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,610,836on Nov. 3, 2009, which claims the benefit of and priority from a numberof U.S. Provisional Patent Applications including Ser. No. 60/225,201,filed Aug. 14, 2000;

Ser. No. 11/811,719, filed Jun. 11, 2007, now U.S. Pat. No. 7,832,314which is a continuation of Ser. No. 11/061,162, filed Feb. 18, 2005,issuing as U.S. Pat. No. 7,228,772 on Jun. 12, 2007, which is acontinuation of Ser. No. 09/929,244, filed Aug. 13, 2001, issuing asU.S. Pat. No. 6,857,345 on Feb. 22, 2005, which in turn claimed thebenefit of and priority from a number of U.S. Provisional PatentApplications including Ser. No. 60/225,212, filed Aug. 14, 2000;

Ser. No. 12/587,695, filed Oct. 9, 2009, which is a continuation of Ser.No. 09/929,237, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,600,455on Oct. 13, 2009, which claims the benefit of and priority from a numberof U.S. Provisional Patent Applications including Ser. No. 60/225,059,filed Aug. 14, 2000;

Ser. No. 12/661,766, filed Mar. 22, 2010, which is a continuation ofSer. No. 11/810,196, filed Jun. 4, 2007, issuing as U.S. Pat. No.7,681,479 on Mar. 23, 2010, which is a continuation of Ser. No.09/929,234, filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,225,712 onJun. 5, 2007, which claims the benefit of and priority from a number ofU.S. Provisional Patent Applications including Ser. No. 60/225,094,filed Aug. 14, 2000;

Ser. No. 12/655,694, filed Jan. 4, 2010, which is a continuation of Ser.No. 12/079,836, filed Mar. 27, 2008, issuing as U.S. Pat. No. 7,640,837on Jan. 5, 2010, which is a continuation of Ser. No. 09/929,235, filedAug. 13, 2001, issuing as U.S. Pat. No. 7,350,444 on Apr. 1, 2008, whichclaims the benefit of and priority from a number of U.S. Provisionalpatent applications including Ser. No. 60/225,058, filed Aug. 14, 2000;

Ser. No. 12/799,211, filed Apr. 19, 2010, which is a continuation ofSer. No. 12/220,946, filed Jul. 29, 2008, issuing as U.S. Pat. No.7,698,976 on Apr. 20, 2010, which is a continuation of Ser. No.09/929,238, filed Aug. 13, 2001, now abandoned, which claims the benefitof and priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,057, filed Aug. 14, 2000;

Ser. No. 12/288,578, filed Oct. 21, 2008, now abandoned which is acontinuation of Ser. No. 11/447,449, filed Jun. 5, 2006, now abandoned,which is a continuation of Ser. No. 09/676,190, filed Sep. 29, 2000,issuing as U.S. Pat. No. 7,055,417 on Jun. 6, 2006, which in turnclaimed the benefit of and priority from the following U.S. Provisionalpatent applications: Ser. No. 60/182,866, filed Feb. 16, 2000, and Ser.No. 60/157,340, filed Oct. 1, 1999;

Ser. No. 12/590,924, filed Nov. 16, 2009, which is a continuation ofSer. No. 12/154,675, filed May 23, 2008, issuing as U.S. Pat. No.7,617,752 on Nov. 17, 2009, which is a continuation of Ser. No.10/053,390, filed Jan. 16, 2002, issuing as U.S. Pat. No. 7,377,199 onMay 27, 2008, which is a continuation-in-part of a number ofapplications including Ser. No. 09/676,190, filed Sep. 29, 2000, issuingas U.S. Pat. No. 7,055,417 on Jun. 6, 2006; and Ser. No. 10/053,390 alsoclaims the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/270,011, filed Feb. 20, 2001;

Ser. No. 12/313,162, filed Nov. 17, 2008, now U.S. Pat. No. 7,789,002,which is a continuation of Ser. No. 11/348,580, filed Feb. 6, 2006, nowabandoned, which is a continuation of a number of applications includingSer. No. 10/052,705, filed Jan. 16, 2002, issuing as U.S. Pat. No.6,994,004 on Feb. 7, 2006, which in turn claimed the benefit of andpriority from the following U.S. Provisional Patent Applications: Ser.No. 60/270,011, filed Feb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22,2001, Ser. No. 60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177,filed Mar. 2, 2001, and Ser. No. 60/273,178, filed Mar. 2, 2001; andSer. No. 11/348,580 also claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/667,485, filed Mar. 31, 2005;and Ser. No. 12/313,162 is also a continuation of Ser. No. 11/098,984,filed Apr. 4, 2005, issuing as U.S. Pat. No. 7,353,737 on Apr. 8, 2008,which is a continuation of a Ser. No. 09/929,238, filed Aug. 13, 2001,now abandoned Ser. No. 10/047,066, filed Jan. 14, 2002, issuing as U.S.Pat. No. 6,945,148 on Sep. 20, 2005, and Ser. No. 10/051,782, filed Jan.15, 2002, issuing as U.S. Pat. No. 6,877,410 on Apr. 12, 2005;

Ser. No. 12/661,993, filed Mar. 26, 2010, which is a continuation ofSer. No. 11/982,972, filed Nov. 5, 2007, issuing as U.S. Pat. No.7,685,912 on Mar. 30, 2010, which is a continuation of Ser. No.10/932,339, filed Sep. 1, 2004, issuing as U.S. Pat. No. 7,290,472 onNov. 6, 2007, which is a continuation of Ser. No. 10/047,066, filed Jan.14, 2002, issuing as U.S. Pat. No. 6,945,148 on Sep. 20, 2005, which inturn claimed the benefit of and priority from the following U.S.Provisional Patent Applications: Ser. No. 60/270,011, filed Feb. 20,2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No. 60/270,942,filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2, 2001, Ser. No.60/273,178, filed Mar. 2, 2001, and Ser. No. 60/273,902, filed Mar. 6,2001; and Ser. No. 10/932,339 filed Sep. 1, 2004, now U.S. Pat. No.7,290,472, is also a continuation of Ser. No. 10/050,085, filed Jan. 14,2002, now abandoned;

Ser. No. 10/100,211, filed Mar. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/275,583, filed Mar. 13, 2001;

Ser. No. 11/256,757, filed Oct. 24, 2005, which is a continuation ofSer. No. 09/955,418, filed Sep. 17, 2001, issuing as U.S. Pat. No.6,957,601 on Oct. 25, 2005, which in turn claimed the benefit of andpriority to a number of U.S. Provisional Patent Applications, including:Ser. No. 60/233,459, filed Sep. 18, 2000, Ser. No. 60/270,011, filedFeb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 13,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, Ser. No. 60/273,902,filed Mar. 6, 2001, Ser. No. 60/275,594, filed Mar. 13, 2001, Ser. No.60/275,595, filed Mar. 13, 2001, Ser. No. 60/279,313, filed Mar. 27,2001, Ser. No. 60/292,081, filed May 17, 2001, Ser. No. 60/292,100,filed May 17, 2001, Ser. No. 60/298,207, filed Jun. 13, 2001, Ser. No.60/302,937, filed Jul. 2, 2001, Ser. No. 60/302,916, filed Jul. 3, 2001,Ser. No. 60/306,202, filed Jul. 18, 2001, Ser. No. 60/307,756, filedJul. 25, 2001, Ser. No. 60/308,492, filed Jul. 27, 2001, and Ser. No.60/312,141, filed Aug. 13, 2001;

Ser. No. 10/146,527, filed May 15, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/292,100,filed May 17, 2001;

Ser. No. 12/586,469, filed Sep. 21, 2009, which is a continuation ofSer. No. 11/702,330, filed Feb. 5, 2007, issuing as U.S. Pat. No.7,591,210 on Sep. 22, 2009, which is a continuation of Ser. No.10/189,031, filed Jul. 2, 2002, issuing as U.S. Pat. No. 7,171,879 onFeb. 6, 2007, which claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/302,937, filed Jul. 2, 2001;

Ser. No. 11/208,214, filed Aug. 19, 2005, now U.S. Pat. No. 7,784,507,which is a continuation of Ser. No. 10/251,576, filed Sep. 20, 2002, nowabandoned, which is a continuation of Ser. No. 10/197,975, filed Jul.18, 2002, now abandoned and which claimed the benefit of and priority toU.S. Provisional Patent Application Ser. No. 60/323,975, filed Sep. 21,2001, and Ser. No. 11/208,214 is also a continuation of Ser. No.09/676,190, filed Sep. 29, 2000, issuing as U.S. Pat. No. 7,055,417 onJun. 6, 2006, which in turn claimed the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/157,340, filed Oct. 1,1999 and Ser. No. 60/182,866, filed Feb. 16, 2000;

Ser. No. 12/231,080, filed Aug. 29, 2008, which is a continuation ofSer. No. 11/487,717, filed Jul. 17, 2006, issuing as U.S. Pat. No.7,421,315, on Sep. 2, 2008, which is a continuation of U.S. patentapplication Ser. No. 10/292,607, filed Nov. 12, 2002, issued as U.S.Pat. No. 7,077,039 on Jul. 18, 2006, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/335,970,filed Nov. 13, 2001;

Ser. No. 12/655,962, filed Jan. 11, 2010, which is a continuation ofSer. No. 12/313,277, filed Nov. 17, 2008, issuing as U.S. Pat. No.7,644,645 on Jan. 12, 2010, which is a continuation of Ser. No.10/345,630, filed Jan. 15, 2003, now abandoned which claims the benefitof and priority from U.S. Provisional Patent Application Ser. No.60/349,989, filed Jan. 16, 2002;

Ser. No. 12/658,759, filed Feb. 12, 2010, which is a continuation ofSer. No. 11/787,471, filed Apr. 17, 2007, issuing as U.S. Pat. No.7,661,343 on Feb. 16, 2010, which is a continuation of Ser. No.10/341,260, filed Jan. 13, 2003, now abandoned, which claims the benefitof and priority from U.S. Provisional Patent Application Ser. No.60/351,797, filed Jan. 25, 2002;

Ser. No. 11/647,676, filed Dec. 29, 2006, now U.S. Pat. No. 7,836,804,which is a continuation of Ser. No. 10/923,290, filed Aug. 20, 2004,issuing as U.S. Pat. No. 7,472,634 on Jan. 6, 2009, which claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/496,550, filed Aug. 20, 2003;

Ser. No. 12/079,820, filed Mar. 27, 2008, now U.S. Pat. No. 7,485,258,which is a continuation of Ser. No. 10/923,273, filed Aug. 20, 2004,issuing as U.S. Pat. No. 7,350,445 on Apr. 1, 2008, which claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/496,574, filed Aug. 20, 2003;

Ser. No. 12/454,569, filed May 18, 2009, which is a continuation of Ser.No. 11/027,600, filed Dec. 31, 2004, issuing as U.S. Pat. No. 7,536,238on May 19, 2009, which claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/533,791, filed Dec. 31, 2003;

Ser. No. 12/799,915, filed May 3, 2010, which is a continuation of Ser.No. 12/322,069, filed Jan. 26, 2009, issuing as U.S. Pat. No. 7,707,918on May 4, 2010, which is a continuation of U.S. patent application Ser.No. 11/107,499, filed Apr. 15, 2005, issuing as U.S. Pat. No. 7,481,140on Jan. 27, 2009;

Ser. No. 12/077,576, filed Mar. 19, 2008, which is a continuation ofSer. No. 11/027,254, filed Dec. 31, 2004, now abandoned, which claimsthe benefit of and priority from U.S. Provisional Patent ApplicationSer. No. 60/533,852, filed Dec. 31, 2003;

Ser. No. 12/799,920, filed May 3, 2010, which is a continuation of Ser.No. 11/026,114, filed Dec. 31, 2004, issuing as U.S. Pat. No. 7,707,920on May 4, 2010, which claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/533,811, filed Dec. 31, 2003;

Ser. No. 11/026,006, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,575, filed Dec. 31, 2003;

Ser. No. 11/045,972, filed Jan. 28, 2005, now U.S. Pat. No. 7,827,890,which claims the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/540,377, filed Jan. 29, 2004; and

Ser. No. 12/454,730, filed May 20, 2009, which is a continuation of Ser.No. 11/395,502, filed Mar. 31, 2006, now abandoned which claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/667,485, filed Mar. 31, 2005.

FIELD

The present disclosure relates to safety systems and more particularlyto methods for enhancing the safety of power equipment.

BACKGROUND

Power equipment such as table saws, miter saws and other woodworkingmachinery include cutting tools like circular saw blades and knifeblades that present a risk of injury to a user of the equipment.Accordingly, safety features or systems are incorporated with powerequipment to minimize the risk of injury. Probably the most commonsafety feature is a guard that physically blocks an operator from makingcontact with dangerous components of machinery, such as belts, shafts orblades. In many cases, guards effectively reduce the risk of injury,however, there are many instances where the nature of the operations tobe performed precludes using a guard that completely blocks access tohazardous machine parts.

Other safety systems try to prevent or minimize injury by detecting andreacting to an event. For instance, U.S. Pat. Nos. 3,953,770, 4,075,961,4,470,046, 4,532,501 and 5,212,621, the disclosures of which areincorporated herein by reference, disclose radio-frequency safetysystems which utilize radio-frequency signals to detect the presence ofa user's hand in a dangerous area of the machine and thereupon preventor interrupt operation of the machine. U.S. Pat. Nos. 3,785,230 and4,026,177, the disclosures of which are herein incorporated byreference, disclose a safety system for use on circular saws to stop theblade when a user's hand approaches the blade. The system uses the bladeas an antenna in an electromagnetic proximity detector to detect theapproach of a user's hand prior to actual contact with the blade. Upondetection of a user's hand, the system engages a brake using a standardsolenoid.

U.S. Pat. No. 4,117,752, which is herein incorporated by reference,discloses a braking system for use with a band saw, where the brake istriggered by actual contact between the user's hand and the blade.However, the system described for detecting blade contact does notappear to be functional to accurately and reliably detect contact.Furthermore, the system relies on standard electromagnetic brakesoperating off of line voltage to stop the blade and pulleys of the bandsaw. It is believed that such brakes would take 50 ms-1 s to stop theblade. Therefore, the system is too slow to stop the blade quicklyenough to avoid serious injury.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a machine with a fast-actingsafety system.

FIG. 2 is a schematic diagram of an exemplary safety system in thecontext of a machine having a circular blade.

FIG. 3 is a schematic side view of a table saw with a retraction system.

FIG. 4 is a schematic side view of a second side of a table saw with aretraction system.

FIG. 5 is a schematic, side view of a saw with another embodiment of aretraction system.

FIG. 6 is a section view of a retraction system using a deformablebushing.

FIG. 7 is a schematic side view of a miter saw with a retraction system.

FIG. 8 is a section view of the miter saw shown in FIG. 7.

FIG. 9 shows another embodiment of a miter saw with a retraction system.

FIG. 10 shows a schematic drawing of a retraction system using a springto retract a cutting tool.

FIG. 11 is a sectional view of the retraction system shown in FIG. 10.

FIG. 12 also is a sectional view of the retraction system shown in FIG.10.

FIG. 13 is a schematic view of a band saw with a retraction system.

FIG. 14 is a top view of a roller used in the system shown in FIG. 13.

FIG. 15 shows an explosive charge that can be triggered by a firingsubsystem.

FIG. 16 is a schematic side elevation view of a miter saw having analternative exemplary safety system configured to stop the miter sawpivot arm as well as the blade.

FIG. 17 is a magnified side view of an exemplary retraction assemblyaccording to the present invention.

FIG. 18 is a magnified cross-sectional view of the retraction assemblyof FIG. 17.

FIG. 19 is a magnified, fragmentary view of the retraction assembly ofFIG. 17, showing the restraining mechanism in detail.

FIG. 20 is similar to FIG. 18 except that the clamping device is shownpivoted to the locked position.

FIG. 21 is similar to FIG. 20 except that the housing is shown pushedupward relative to the brace member. For clarity, the components of therestraining member are not shown.

DETAILED DESCRIPTION

A machine that may incorporate a retraction system according to thepresent disclosure is shown schematically in FIG. 1 and indicatedgenerally at 10. Machine 10 may be any of a variety of differentmachines adapted for cutting workpieces, such as wood, including a tablesaw, miter saw (chop saw), radial arm saw, circular saw, band saw,jointer, planer, etc. Machine 10 includes an operative structure 12having a cutting tool 14 and a motor assembly 16 adapted to drive thecutting tool. Machine 10 also includes a safety system 18 configured tominimize the potential of a serious injury to a person using machine 10.Safety system 18 is adapted to detect the occurrence of one or moredangerous conditions during use of machine 10. If such a dangerouscondition is detected, safety system 18 is adapted to engage operativestructure 12 to limit any injury to the user caused by the dangerouscondition.

Machine 10 also includes a suitable power source 20 to provide power tooperative structure 12 and safety system 18. Power source 20 may be anexternal power source such as line current, or an internal power sourcesuch as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of machine 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms, depending on the type of machine 10. For example,operative structure 12 may include a stationary housing configured tosupport motor assembly 16 in driving engagement with cutting tool 14.Alternatively, operative structure 12 may include a movable structureconfigured to carry cutting tool 14 between multiple operatingpositions. As a further alternative, operative structure 12 may includeone or more transport mechanisms adapted to convey a workpiece towardand/or away from cutting tool 14.

Motor assembly 16 includes one or more motors adapted to drive cuttingtool 14. The motors may be either directly or indirectly coupled to thecutting tool, and may also be adapted to drive workpiece transportmechanisms. Cutting tool 14 typically includes one or more blades orother suitable cutting implements that are adapted to cut or removeportions from the workpieces. The particular form of cutting tool 14will vary depending upon the various embodiments of machine 10. Forexample, in table saws, miter saws, circular saws and radial arm saws,cutting tool 14 will typically include one or more circular rotatingblades having a plurality of teeth disposed along the perimetrical edgeof the blade. For a jointer or planer, the cutting tool typicallyincludes a plurality of radially spaced-apart blades. For a band saw,the cutting tool includes an elongate, circuitous tooth-edged band.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of machine 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the machine. The control subsystem is configured tocontrol machine 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous, ortriggering, conditions during use of machine 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to, or in contact with, a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. Provisional PatentApplication Ser. No. 60/182,866, the disclosure of which is hereinincorporated by reference. In some embodiments, detection subsystem 22may inform control subsystem 26 of the dangerous condition, which thenactivates reaction subsystem 24. In other embodiments, the detectionsubsystem may be adapted to activate the reaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of machine 10 and/or the dangerous condition that is detected. Forexample, reaction subsystem 24 may be configured to do one or more ofthe following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, or retract the cutting tool from its operatingposition, etc. The reaction subsystem may be configured to take acombination of steps to protect the user from serious injury. Placementof a barrier between the cutting tool and teeth is described in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,206,entitled “Cutting Tool Safety System,” filed Aug. 14, 2000 by SD3, LLC,the disclosure of which is herein incorporated by reference.

The configuration of reaction subsystem 24 typically will vary dependingon which action(s) are taken. In the exemplary embodiment depicted inFIG. 1, reaction subsystem 24 is configured to stop the movement ofcutting tool 14 and includes a brake mechanism 28, a biasing mechanism30, a restraining mechanism 32, and a release mechanism 34. Brakemechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of machine 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of safety system 18 is shown. System 18 isconfigured to engage an operative structure having a cutting tool in theform of a circular blade 40 mounted on a rotating shaft or arbor 42.Blade 40 includes a plurality of cutting teeth (not shown) disposedaround the outer edge of the blade. As described in more detail below,braking mechanism 28 is adapted to engage the teeth of blade 40 and stopthe rotation of the blade. U.S. Provisional Patent Application Ser. No.60/225,210, entitled “Translation Stop For Use In Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosure of which is hereinincorporated by reference, describes other systems for stopping themovement of the cutting tool. U.S. Provisional Patent Application Ser.No. 60/225,058, entitled “Table Saw With Improved Safety System,” filedAug. 14, 2000 by SD3, LLC, and U.S. Provisional Patent Application Ser.No. 60/225,057, entitled “Miter Saw With Improved Safety System,” filedAug. 14, 2000 by SD3, LLC, the disclosures of which are hereinincorporated by reference, describe safety system 18 in the context ofparticular types of machines 10.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of machine 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,200, entitled “Contact Detection System ForPower Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S. ProvisionalPatent Application Ser. No. 60/225,211, entitled “Apparatus And MethodFor Detecting Dangerous Conditions In Power Equipment,” filed Aug. 14,2000 by SD3, LLC, the disclosures of which are herein incorporated byreference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls, etc.Control subsystem 26 also includes a logic controller 50 connected toreceive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as blade motion sensors,workpiece sensors, etc. In any event, the logic controller is configuredto control operative structure 12 in response to the user's inputsthrough instruments 48. However, upon receipt of a contact detectionsignal from detection subsystem 22, the logic controller overrides thecontrol inputs from the user and activates reaction subsystem 24 to stopthe motion of the blade. Various exemplary embodiments andimplementations of control subsystem 26 are described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,059, entitled “LogicControl For Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC,and U.S. Provisional Patent Application Ser. No. 60/225,094, entitled“Motion Detecting System For Use In Safety System For Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosures of which are hereinincorporated by reference.

In the exemplary implementation, brake mechanism 28 includes a pawl 60mounted adjacent the edge of blade 40 and selectively moveable to engageand grip the teeth of the blade. Pawl 60 may be constructed of anysuitable material adapted to engage and stop the blade. As one example,the pawl may be constructed of a relatively high strength thermoplasticmaterial such as polycarbonate, ultrahigh molecular weight polyethylene(UHMW) or Acrylonitrile Butadiene Styrene (ABS), etc., or a metal suchas aluminum, etc. It will be appreciated that the construction of pawl60 will vary depending on the configuration of blade 40. In any event,the pawl is urged into the blade by a biasing mechanism in the form of aspring 66. In the illustrative embodiment shown in FIG. 2, pawl 60 ispivoted into the teeth of blade 40. It should be understood that slidingor rotary movement of pawl 60 might also be used. The spring is adaptedto urge pawl 60 into the teeth of the blade with sufficient force togrip the blade and quickly bring it to a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism in the form of a fusible member 70. The fusible member isconstructed of a suitable material adapted to restrain the pawl againstthe bias of spring 66, and also adapted to melt under a determinedelectrical current density. Examples of suitable materials for fusiblemember 70 include NiChrome wire, stainless steel wire, etc. The fusiblemember is connected between the pawl and a contact mount 72. Preferably,fusible member 70 holds the pawl relatively close to the edge of theblade to reduce the distance the pawl must travel to engage the blade.Positioning the pawl relatively close to the edge of the blade reducesthe time required for the pawl to engage and stop the blade. Typically,the pawl is held approximately 1/32-inch to ¼-inch from the edge of theblade by fusible member 70, however other pawl-to-blade spacings mayalso be used within the scope of the invention.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,056, entitled “Firing Subsystem ForUse In Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC, U.S.Provisional Patent Application Ser. No. 60/225,170, entitled“Spring-Biased Brake Mechanism for Power Equipment,” filed Aug. 14, 2000by SD3, LLC, and U.S. Provisional Patent Application Ser. No.60/225,169, entitled “Brake Mechanism For Power Equipment,” filed Aug.14, 2000 by SD3, LLC, the disclosures of which are herein incorporatedby reference.

Other systems can also be used to shift the pawl or pawls into contactwith the blade, and firing system 76 may also be used to trigger someaction other than burning a fusible member. For example, firing system76 can fire a small explosive charge to move a pawl. FIG. 15 shows arelatively small, self-contained explosive charge 660 in the form of asquib or detonator that can be used to drive pawl 60 against a blade. Anexample of a suitable explosive charge is an M-100 detonator available,for example, from Stresau Laboratory, Inc., of Spooner, Wis. Althoughany suitable explosive charge system may be used, the exemplaryembodiment preferably uses a self-contained charge or squib to increasesafety and focus the force of the explosion along the direction ofmovement of the pawl. A trigger line 662 extends from the charge, and itmay be connected to firing system 76 to trigger detonation.

Explosive charge 660 can be used to move pawl 60 by inserting the chargebetween the pawl and a stationary block 664 adjacent the charge. Whenthe charge detonates, the pawl is pushed away from the block. Acompression spring 66 is placed between the block and pawl to ensure thepawl does not bounce back from the blade when the charge is detonated.Prior to detonation, the pawl is held away from the blade by thefriction-fit of the charge in both the block and pawl. However, theforce created upon detonation of the charge is more than sufficient toovercome the friction fit. Alternatively, the pawl may be held away fromthe blade by other mechanisms such as a frangible member, gravity, aspring between the pawl and block, etc.

Firing system 76 may also trigger a DC solenoid, which can beover-driven with a current surge to create a rapid displacement, apressurized air or gas cylinder to supply the pressure in place of thespring or charge, or an electromagnet to either repel the pawl againstthe blade or to release a spring-loaded pawl toward the blade.

It will be appreciated that activation of the brake mechanism willrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically must be replaced beforethe safety system is ready to be used again. Thus, it may be desirableto construct one or more portions of safety system 18 in a cartridgethat can be easily replaced. For example, in the exemplaryimplementation depicted in FIG. 2, safety system 18 includes areplaceable cartridge 80 having a housing 82. Pawl 60, spring 66,fusible member 70 and contact mount 72 are all mounted within housing82. Alternatively, other portions of safety system 18 may be mountedwithin the housing. In any event, after the reaction system has beenactivated, the safety system can be reset by replacing cartridge 80. Theportions of safety system 18 not mounted within the cartridge may bereplaced separately or reused as appropriate. Various exemplaryembodiments and implementations of a safety system using a replaceablecartridge are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,201, entitled “Replaceable Brake MechanismFor Power Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S.Provisional Patent Application Ser. No. 60/225,212, entitled “BrakePositioning System,” filed Aug. 14, 2000 by SD3, LLC, the disclosures ofwhich are herein incorporated by reference.

While one particular implementation of safety system 18 has beendescribed, it will be appreciated that many variations and modificationsare possible within the scope of the invention. Many such variations andmodifications are described in U.S. Provisional Patent Application Ser.Nos. 60/182,866 and 60/157,340, the disclosures of which are hereinincorporated by reference.

As briefly mentioned above, reaction subsystem 24 can be configured witha retraction system to retract or move a cutting tool away from thepoint of accidental contact with a user. Moving away from the point ofaccidental contact reduces the time the cutting tool is in contact withthe user, thereby minimizing any injury to the user. Moving the cuttingtool away from the point of accidental contact also prevents the cuttingtool from moving toward the user, which could increase any injury to theuser. For example, a spinning blade in a miter saw has substantialangular momentum, and that angular momentum could cause the blade tomove downward toward a user when a brake pawl hits the blade. Thespinning blade in a table saw also has substantial angular momentum thatcould cause the blade to move upward toward a user when a brake pawlhits the blade, depending on the position of the brake, the weight ofthe blade and the amount of play in the structure supporting the blade.Preventing any such movement lessens the potential injury to the user. Aretraction system may be used in addition to or instead of other safetymechanisms.

FIGS. 3 and 4 show side views of a table saw configured with both aretraction system and a braking mechanism. A blade 300 is mounted on anarbor 301 to spin in the direction of arrow 302. A table 303 (not shownin FIG. 4), which defines the work surface or cutting region for thetable saw, is adjacent the blade and the blade extends above the table.A support structure 304 may support blade 300 and arbor 301 in any knownway, or as described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,058, titled “Table Saw with Improved SafetySystem,” filed Aug. 14, 2000.

Blade 300 is configured to pivot up and down so that a user can positionthe blade to extend above the table as needed. The blade pivots around apin 305. A user may pivot the blade to adjust its position by turning ashaft 306 on which a worm gear 307 is mounted. The worm gear is mountedon the shaft so that it turns with the shaft, but so that it may slideon the shaft when necessary, as explained below. Worm gear 307 ismounted on shaft 306 like a collar, with the shaft extending through alongitudinal hole in the worm gear. The worm gear is held in placeduring normal operation of the saw by a spring clip 308, which ispositioned in a groove or channel 309 on the worm gear and which alsoengages a detent or shoulder on shaft 306 to hold the worm gear inplace. The worm gear engages an arcuate rack 310 that supports an arborblock 311, which in turn supports arbor 301 and blade 300. Thus, when auser turns shaft 306, such as by turning a knob attached to the shaft(not shown), worm gear 307 moves arbor block 311 and the blade up ordown, depending on the direction that the worm gear is turned.

A brake cartridge 312 is mounted in the saw adjacent blade 300. Thebrake cartridge includes a pawl 314 biased toward blade 300 by a spring316. The pawl is held away from blade 300 by a release mechanism 318, asdescribed generally above and as described in more detail in U.S.Provisional Patent Application Ser. No. 60/225,170, entitled“Spring-Biased Brake Mechanism for Power Equipment,” U.S. ProvisionalPatent Application Ser. No. 60/225,169, entitled “Brake Mechanism forPower Equipment,” U.S. Provisional Patent Application Ser. No.60/225,201, entitled “Replaceable Brake Mechanism for Power Equipment,”and U.S. Provisional Patent Application Ser. No. 60/225,212, entitled“Brake Positioning System,” all filed Aug. 14, 2000. The cartridge isconfigured so that the release mechanism releases the pawl into theblade upon the receipt of a detection signal, as explained generallyabove and as explained in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,056, titled “Firing Subsystem for use in aFast-Acting Safety System,” filed Aug. 14, 2000.

Brake cartridge 312 is positioned on the blade's pivot axis so that pawl314 can move around pin 305. Thus, when pawl 314 hits the blade, theangular momentum of the blade is transferred to the arbor block, and theblade, arbor block, rack and cartridge try to retract or move down inthe direction of arrow 320. Alternatively, the cartridge may bepositioned on a pin different from pin 305, but that still pivots withthe blade.

The blade will move down to the extent permitted by the contact betweenrack 310 and worm gear 307. If the worm gear is fixed in place, thedownward movement of the blade may strip teeth on the rack and/or wormgear, and may prevent the blade from moving down as far as desired. Inthe embodiment shown in FIGS. 3 and 4, the worm gear is adapted to snapfree and move on shaft 306 when the pawl hits the blade.

When the pawl hits the blade, the resultant angular momentum impulsecauses spring clip 308 to snap loose, allowing the worm gear to slidedown the shaft toward an end 322 of the shaft. The spring clip snapsloose because the rack moves down when the blade is stopped, and therack contacts the worm gear and forces the worm gear to move. The forceof the rack against the worm gear causes the spring clip to snap loose.The worm gear is put back in place by moving it back along shaft 306until the spring clip snaps into place on the shaft.

The table saw shown in FIGS. 3 and 4 also includes a support 326configured with a seat or region 328 in which is placed animpact-absorbing material 330. The support is positioned under the arborand arbor block so that when the blade retracts, the arbor block strikesimpact-absorbing material 330. Support 326 and impact absorbing material330 act as a barrier to stop the downward movement of the blade. Thesupport is positioned so that blade 300 may retract a sufficientdistance. The impact-absorbing material can be any one of a number ofcushioning materials, such as rubber, dense foam, plastic, etc. Onematerial found to be suitable is available under the part numberC-1002-06 from AearoEAR, of Indianapolis, Ind. Alternatively,impact-absorbing material 330 may be attached to the undersurface of thearbor block instead of on support 326. Additionally, support 326 maytake many forms. In fact, shaft 306 may be configured and positioned sothat it provides a surface to stop the downward movement of the blade.

FIG. 4 also shows a splitter 335 that extends above table 303 behindblade 300 to prevent kickback. A blade guard may also substantiallyenclose blade 300. FIG. 4 further shows a housing 337 for electroniccomponents relating to the safety system, and a motor mount 339, whichare not shown in FIG. 3.

In the construction described above, the angular momentum of the bladecauses the blade, arbor block and cartridge to all pivot down away fromthe cutting region when the pawl strikes the blade. Thus, the angularmomentum of the blade causes the retraction. Blade 300 is permitted tomove downward a sufficient distance so that the blade is completelyretracted. In independent experiments, the safety system depicted inFIGS. 3 and 4 and described above has been shown to retract the bladecompletely below table 303 within approximately 14 milliseconds aftercontact is detected. Indeed the downward motion of the blade duringretraction is too fast to detect with the human eye, i.e., the bladedisappears below table 303 with no discernable transition or downwardmotion. The ability of the blade to retract minimizes any injury fromaccidental contact with the blade.

FIG. 5 shows another embodiment of a retraction system used with a brakepawl. A saw 331 includes a blade 300 and a brake cartridge 312 housing abrake pawl 314. The cartridge and pawl are mounted to the frame of thesaw by a pin 332. The pin is mounted to the saw in such a way that itmay not pivot up and down with the blade. When the blade hits the pawl,the blade climbs down the pawl, or in other words, moves generallyaround the point of contact with the pawl. The pawl and blade do notpivot downward together, as in the embodiment shown in FIGS. 3 and 4,because the pawl is fixed to the frame of the saw. In this embodiment,the blade retracts by “climbing” down the pawl.

Another embodiment of a retraction system comprises a compressiblebushing. Typically, a blade 300 in a table saw, miter saw or othermachine is mounted to an arbor over a bushing 333, as shown in FIG. 6. Alocking nut, washers and an arbor flange are used to secure the blade tothe arbor. Bushing 333 may be constructed from a material that is softenough to deform when the blade is stopped suddenly. For example,depending on the type of braking system used, a substantial radialimpact load may be transmitted to the arbor when the brake is actuated.A deformable bushing can be used to absorb some of this impact andreduce the chance of damage to the arbor. In addition, properpositioning of the brake in combination with a deformable bushing may beemployed to cause the blade to move away from the user upon activationof the brake. Where a plastic bushing is placed between the blade andthe arbor, the substantial force created by stopping the blade almostinstantly may cause the bushing to deform. Typically, the edge of themounting hole of the blade will bite into the bushing as the bladeattempts to rotate about the pawl. Therefore, if the pawl is mounted atthe back of the blade, then the blade will tend to move downward intothe bushing and away from the user when the pawl engages the blade.

FIGS. 7 and 8 show a miter saw equipped with both a brake and aretraction system. The miter saw is configured with a pivotal motorassembly to allow the blade to move upward into the housing uponengagement with a brake pawl 348. Motor assembly 350 is connected tohousing 352 via pivot bolt 354, allowing the motor assembly to pivotabout bolt 354 in the direction of blade rotation. A spring 356 iscompressed between the motor assembly and an anchor 358 to bias themotor assembly against the direction of blade rotation. The motorassembly may include a lip 360, which slides against a flange 362 on thehousing to hold the end of the motor assembly opposite the pivot boltagainst the housing.

When the saw is in use, spring 356 holds the motor assembly in a normalposition rotated fully counter to the direction of blade rotation.However, once the pawl is released to engage the blade, the motorassembly and blade pivot upward against the bias of the spring. In thisembodiment, the pawl is positioned at the front of the blade so that thepivot bolt 354 is between the pawl and the arbor. This arrangementencourages the blade to move upward into the housing when stopped. Thespring is selected to be sufficiently strong to hold the motor assemblydown when cutting through a workpiece, but sufficiently compressible toallow the blade and motor assembly to move upward when the blade isstopped. Of course, the blade and motor assembly may be configured inany of a variety of ways to at least partially absorb the angularmomentum of the blade.

FIG. 9 shows an alternative configuration of a miter saw adapted to moveaway from an accidental contact with a user by absorbing the angularmomentum of the blade. In this configuration, the miter saw includes twoswing arms 370 and 372. One end 374 of each swing arm 370, 372 isconnected to base 376, and the opposite end 378 of each swing arm isconnected to housing 380, the blade, and/or the motor assembly (notshown). The position of the swing arms relative to each other may varydepending on the swing arm motion desired. In FIG. 9, swing arm 370 isconnected to base 376 somewhat below and forward of swing arm 372.Typically, the motor assembly is rigidly attached to end 378 of swingarm 370, while housing 380 is connected to rotate about end 378 of swingarm 370. End 378 of swing arm 372 is connected only to the housing.Alternatively, the motor assembly may be connected to rotate about end378 of swing arm 370 along with the housing.

The geometry of the configuration shown in FIG. 9 causes the housingand/or motor assembly to rotate as the swing arms pivot. Significantly,when the swing arms move upward, the housing and/or motor assemblyrotate in the same direction in which the blade rotates during cutting.As a result, when a brake pawl engages the blade and transfers theangular momentum of the blade to the housing and/or motor assembly, thehousing and/or motor assembly tend to rotate in the same direction asthe blade. This causes the swing arms to pivot upward, drawing the bladeaway from the workpiece and the user's body. Thus, the miter sawconfiguration illustrated in FIG. 9 is adapted to absorb the angularmomentum of the blade and translate that angular momentum into an upwardforce on the swing arms.

In any of the systems described above, a spring or other force can beused to push the blade away from the point of contact with the user. Thespring could be released by a mechanism similar to the mechanism thatreleases the pawl to strike the blade. FIGS. 10-12 show how a spring maybe used to retract a blade in a table saw. FIG. 10 is a top view andFIGS. 11 and 12 are side views of an arbor block 381 holding an arbor382 used to drive a blade (not shown). Arbor block 381 is pivotallymounted to pin 383 so that the arbor block and blade may pivot up anddown to adjust the position of the blade in the saw.

A segment gear 384, like rack 310 described above in connection withFIGS. 3 and 4, is also mounted on pin 383, and is connected to arborblock 381 in the manner described below, to raise and lower the arbor.Segment gear 384 includes a side portion 385 positioned substantiallyperpendicularly to the plane of arbor block 381, and a top portion 386positioned over arbor block 381. The side portion 385 includes gearteeth 387 to engage a worm gear to raise and lower the arbor block. Sideportion 385 and top portion 386 are connected to each other and movetogether. Top portion 386 extends over the top of the entire arborblock, as shown. The arbor block is constructed with a region toaccommodate top portion 386 so that top portion 386 does not extendsubstantially above the arbor block, which could limit the ability ofthe arbor block and blade to pivot upward when desired, such as bycontacting the underside of a table in a table saw.

A pocket 388 is formed in arbor block 381 to house a spring 389. In theposition shown in FIG. 11, spring 389 is compressed between top portion386 of segment gear 384 and arbor block 381 because the segment gear andarbor block are coupled together.

The segment gear and arbor block are coupled by a compound linkagehaving, as shown in FIG. 12, a first arm 390 attached at one end to thearbor block and at its other end to a second arm 391. The second arm, inturn, is attached to top portion 386 of segment gear 384, as shown.First and second arms 390 and 391 are hingedly connected to each other,and to the arbor block and segment gear. The arms are configured so thatthe force of the spring pushing apart the arbor block and the topportion of the segment gear biases the first and second arms in such away that the arms want to move. A fusible member 392, which may take theform of a wire as described above, restrains the arms from movement. Ofcourse, numerous different linkages may be used, and numerous types andconfigurations of fusible members or other release mechanisms may beused. The linkage may be selected to provide a sufficient mechanicaladvantage so that the arbor block and top portion of the segment gearmay be held together with as thin a fusible member as possible, so thatthe fusible member may be burned as easily as possible. Variousanalogous compound linkages are described in U.S. Provisional PatentApplication Ser. No. 60/225,170, entitled “Spring-Biased Brake Mechanismfor Power Equipment,” filed Aug. 14, 2000. The fusible member may beburned by a system as described above, or as described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,056, entitled“Firing Subsystem for Use in Fast-Acting Safety System,” filed Aug. 14,2000, the disclosure of which is hereby incorporated by reference. Thecompound linkage and the fusible member are preferably configured sothat they accommodate spring forces of 100 to 500 pounds or more. Inother embodiments, the restraining member may include various mechanicallinkages, or may be part of various actuators, and those linkages and/oractuators may be released or fired by solenoids, gas cylinders,electromagnets, and/or explosives, as explained in U.S. ProvisionalPatent Application Ser. No. 60/302,916, entitled “Actuators for Use inFast-Acting Safety Systems,” filed Jul. 3, 2001, the disclosure of whichis hereby incorporated by reference.

When the fusible member is burned, the compound linkage is free to move,and the spring pushes arbor block 381 down, away from top portion 386 ofthe segment gear, as shown by the dashed lines in FIG. 11, therebyretracting the blade. The stronger the spring, the faster the blade willbe retracted. The segment gear does not move because it is coupledthrough teeth 387 to a worm gear or some other structure.

Retracting a blade by a spring or some other force may be thought of asdirect retraction. A spring or other force may be used with some otherretraction system to increase the speed that a cutting tool retracts, ora spring or other force may be used as the sole means of retraction. Thesystems for direct retraction described above may be used on variouspieces of equipment, including table saws, miter saws and band saws.

FIG. 13 is a schematic diagram of a system to retract the blade of aband saw. Typically, a band saw includes a main housing enclosing a pairof vertically spaced-apart wheels. The perimeter of each wheel is coatedor covered in a high-friction material such as rubber, etc. A relativelythin, continuous loop blade tightly encircles both wheels. A workpieceis cut by passing it toward the blade in a cutting zone between thewheels. The workpiece is passed toward the blade on a table, which formsthe bottom of the cutting zone.

The band saw shown in FIG. 13 includes roller 393 positioned adjacentthe blade. The roller is configured to contact the blade and push theblade away from the point of accidental contact with a user. Inaddition, the roller may be configured to push the blade off the wheels,thereby stopping the motion of the blade. A top view of the roller isshown in FIG. 14 pushing against a blade in the direction of the arrow.The roller may be part of a cartridge, and may be released into theblade just as the pawls described above are released. The roller shouldhave a diameter large enough so that the roller can roll over the teethof the blade.

The systems for direct retraction of a cutting tool may also beimplemented on hand-held circular saws. Such saws typically include abase plate that contacts a workpiece during sawing. The base platesupports the saw on the workpiece. The base plate may be configured sothat it is pushed down when the blade contacts a user. The result ofthat action is to effectively retract the blade because the base platewould push the user away from the blade.

FIG. 16 illustrates an exemplary miter saw 89 having an alternativeembodiment of safety system 18 configured to at least partially retractthe pivot arm in the event of contact between the blade and the user'sbody.

Exemplary miter saw 89 includes a base assembly 90 adapted to support aworkpiece (not shown) during cutting. Typically, one or more fences 92are mounted on base assembly 90 and adapted to prevent the workpiecefrom shifting across the base assembly during cutting. Operativestructure 12 is coupled to base assembly 90 and includes a platen 94, atilt mechanism 96, and a pivot arm 98. Platen 94 is coupled to baseassembly 90 and rotatable, relative to the base assembly, about the axisindicated at A. Tilt mechanism 96 is coupled to platen 94. At least aportion of the tilt mechanism is rotatable, relative to base assembly90, about the axis indicated at B. Pivot arm 98 is coupled to tiltmechanism 96 and selectively pivotal toward and away from base assembly90, as illustrated in FIG. 16. Typically, the pivot arm is biased upwardaway from base assembly 90 by a spring or other suitable mechanism.

Motor assembly 16 is mounted on pivot arm 98 and includes at least onemotor 100 and a control handle 102. Blade 40 is coupled to an arborshaft (not shown) that is rotatably driven by motor 100. Control handle102 includes one or more controls (not shown) that are operable by auser to control motor 100. A user brings blade 40 into contact with aworkpiece by grasping control handle 102 and pulling pivot arm 98downward against the upward bias from a nominal position (indicatedgenerally by dash lines in FIG. 16), toward base assembly 90. Once thecutting operation is completed, the user allows the pivot arm to pivotupward toward the nominal position.

It will be appreciated by those of skill in the art that the miter sawconfiguration depicted in FIG. 16 and described above is one commonlyreferred to as a “compound miter saw,” which allows a user to make acompound (i.e., both mitered and beveled) cut in a workpiece byadjusting the position of platen 94 and/or tilt mechanism 96. However,there are many other miter saw configurations known to those of skill inthe art which are also suitable for use with the present invention.Thus, it will be understood that the particular miter saw configurationsdepicted and described herein are provided to illustrate exemplaryembodiments of the invention, and should not be interpreted to limit thescope or application of the present invention.

Although not shown in FIG. 16, detection subsystem 22 and controlsubsystem 26 may be mounted at any desired location on miter saw 89 andconfigured to detect contact between blade 40 and a user's body asdescribed above and in the references incorporated herein.Alternatively, the detection and control subsystems may be configured todetect contact between the user's body and some other portion of themiter saw such as a guard, etc. Upon receiving an activation signal, afirst portion 104 of reaction subsystem 24 is configured to stop therotation of blade 40, while a second portion 106 of the reactionsubsystem is configured to move pivot arm 98 upward away from the baseassembly. In the exemplary embodiment, first portion 104 includes abrake pawl 60 mounted in a cartridge 80, such as described above and inthe incorporated references. Brake pawl 60 is selectively pivotal intoblade 40 to stop the rotation of the blade. Alternatively, the firstportion may employ other brake mechanisms such as described in theincorporated references. As a further alternative, first portion 104 maybe omitted so that the rotation of blade 40 is not stopped in responseto the occurrence of a dangerous condition.

In any event, second portion 106 retracts the pivot arm upward farenough to remove the blade from contact with the user's body.Preferably, the second portion is configured to move the pivot armupward at least ⅛-inch, more preferably at least ¼-inch, and mostpreferably at least ½-inch or more. In embodiments where the reactionsubsystem is configured to stop the rotation of blade 40, the secondportion preferably retracts the pivot arm before or at the same time theblade is stopped. This prevents the pivot arm from moving downward as aresult of angular momentum transferred to the pivot arm from the blade.The second portion of the reaction subsystem may be triggered prior tothe first portion, or the second portion may be configured to engage thepivot arm more quickly than the brake pawl engages the blade.

Second portion 106 of exemplary reaction subsystem 24 includes a bracemember 108 and a retraction assembly 110. Brace member 108 is pivotallycoupled to tilt mechanism 96 at 105. Retraction assembly 110 ispivotally coupled to pivot arm 98 at 107 and configured to slidablyreceive at least a portion of brace member 108. The retraction assemblyis configured to quickly grip or lock onto the brace member and urge thepivot arm upward upon receipt of an actuation signal from controlsubsystem 26. Once the retraction assembly has been triggered, pivot arm98 is prevented from further downward movement toward base assembly 90.While second portion 106 is illustrated as having a single brace memberand a single retraction assembly on one side of miter saw 89, it will beappreciated that the reaction subsystem may alternatively include aplurality of brace members and/or retraction assemblies positioned atselected locations on miter saw 89.

Brace member 108 may take any of a variety of different forms. In theexemplary embodiment, the brace member is an elongate bar or shaftpivotally coupled to tilt mechanism 96. Brace member 108 may beconstructed of any suitably rigid material such as steel, aluminum,plastic, ceramic, etc. The pivotal coupling between the brace member andthe tilt mechanism allows the brace member to pivot as necessary tofollow the retraction assembly as the pivot arm moves toward and awayfrom the base assembly. In the exemplary embodiment, the brace member iscoupled to the tilt mechanism by a ball-joint-rod-end-bearing coupling105, such as are available from a variety of sources including MSCIndustrial Supply Company of Melville, N.Y. Alternatively, other typesof couplings may be used, such as universal couplings, etc.

In the exemplary embodiment, brace member 108 is coupled to an armportion 112 of tilt mechanism 96 that extends outward from the tiltmechanism toward the base assembly. While arm 112 is depicted as anintegral, unitary portion of the tilt mechanism, the arm portion mayalternatively take the form of a separate bracket attached to the tiltmechanism. Alternatively, the arm may be omitted and brace member 108may be coupled to another portion of the tilt mechanism. As furtheralternatives, the brace member may be coupled to a different portion ofmiter saw 10 such as platen 94, fence 92, or base assembly 90, etc. Inany event, the brace member should be relatively rigidly supported toensure that pivot arm 98 is moved upward when retraction assembly 110 istriggered.

Retraction assembly 110 may be coupled to pivot arm 98 in any of avariety of different places. Typically, the retraction assembly andpivot point 107 are disposed to position brace member 108 spaced apartfrom pivot point 114 of arm 98 to increase the moment of the upwardforce applied by reaction subsystem 24 to pivot arm 98. It will beappreciated that the further brace member 108 is positioned from pivotpoint 114, the greater the moment of force provided by the retractionassembly. Thus, it is generally desirable, though not necessary, toposition the brace member as close to the front of miter saw 89 (i.e.,the left side as shown in FIG. 16) as possible without interfering withthe use of the miter saw. Similarly, the pivot point 105 of the bracemember is disposed, relative to the retraction assembly, to orient thebrace member generally perpendicular to the direction in which the pivotarm moves. This arrangement ensures that the downward force on the bracemember is substantially a compression force rather than torque.Alternatively, retraction assembly 110 and pivot point 105 may bedisposed at any selected positions suitable for stopping downwardmovement of pivot arm 98.

Since brace member 108 is coupled to tilt mechanism 96, the brace memberwill rotate along with pivot arm 98 about axis A when the miter saw isadjusted for mitered cuts. Similarly, the brace member will tilt aboutaxis B when the miter saw is adjusted for beveled cuts. Thus, theexemplary configuration of reaction subsystem 24 depicted in FIG. 16allows a user to adjust miter saw 89 throughout its full range ofmovement.

Optionally, reaction subsystem 24 may include one or more positioningmechanisms configured to remove any play or looseness in the couplingsbetween brace member 108 and tilt mechanism 96, and/or the couplingsbetween retraction assembly 110 and pivot arm 98. In situations whereplay or looseness may be present, the positioning mechanism ensures thatthe brace member and retraction assembly do not shift when the reactionsubsystem is triggered.

Turning attention now to FIGS. 17-21, one exemplary embodiment ofretraction assembly 110 is illustrated. Exemplary retraction assembly110 is configured to grip and push downward on brace member 108 to movepivot arm 98 upward in response to an activation signal from controlsubsystem 26. Retraction assembly 110 includes a housing 118 configuredto slidably receive brace member 108. Housing 118 includes a lower wall120, and an upper wall 122 spaced apart from the lower wall. Housing 118also includes a first end wall 124 and a second end wall 126 extendingbetween opposite ends of lower wall 120 and upper wall 122. The lower,upper and end walls are connected together by any suitable mechanismsuch as bolts 127. A pair of side walls 128 (shown in FIG. 16) cover thesides of the lower, upper and end walls to enclose the housing.

Housing 118 is connected to the side of pivot arm 98 by a pivotalcoupling 107 that allows the housing to move relative to the pivot armas needed. Any of a variety of different couplings may be used which areknown to those of skill in the art, such as a shoulder screw, etc. Thepivotal coupling allows housing 118 to move as necessary to maintain aconstant orientation or alignment with the brace member. In embodimentswhere the brace member is connected to a different structure on mitersaw 89 such as platen 94 or fence 92, coupling 107 may be configured toallow the housing to both pivot parallel to the side of the pivot armand tilt away from the pivot arm as needed.

As mentioned above, housing 118 is configured to slide along bracemember 108. Lower wall portion 120 includes an orifice 130 configured toslide over the brace member. Similarly, upper wall portion 122 includesan orifice 132 configured to slide over the brace member. Orifices 130and 132 are generally axially aligned and sized to closely fit aroundthe brace member, thereby maintaining the housing in a uniformorientation relative to the brace member as pivot arm 98 is moved towardand away from the workpiece.

Retraction assembly 110 also includes an actuator 134 configured toselectively grip brace member 108 and push the housing upward. Actuator134 may be any one or a combination of elements, devices or mechanismsconfigured to quickly and securely grip the brace member.

In the exemplary embodiment, actuator 134 includes a clamping device 136adapted to selectively grip the brace member, and a drive mechanism 138adapted to urge the housing upward relative to the clamping device.Clamping device 136 is formed to define an orifice 140 adapted toclosely fit and slide along the brace member. The clamping device ispivotal between a nominal or unactuated position (as shown in FIGS. 17and 18), and an actuated or locked position (as shown in FIG. 20). Whenthe clamping device is in the nominal position, the sides of orifice 140are substantially aligned with the sides of brace member 108 so that theclamping device slides relatively freely along the brace member.Conversely, when the clamping device is pivoted into the locked oractuated position, the sides of orifice 140 press into and bind againstthe brace member to releasably lock the clamping device onto the bracemember. Drive mechanism 138 is disposed between the clamping device andupper wall 122 and configured to push the upper wall away from theclamping device when the clamping device is in the locked position. As aresult, housing 118 and pivot arm 98 are pushed upward relative to thebrace member and base assembly 90.

Clamping device 136 may be constructed of any suitable material adaptedto grip the brace member and support the force exerted by drivemechanism 138. Typically, the clamping device is constructed of amaterial which does not cause damage to brace member 108 when theretraction assembly is triggered. For example, the clamping device andbrace member may each be formed from a relatively rigid material such ashardened steel. Alternatively, the clamping device and/or brace membermay be formed of any of a variety of other suitable materials known tothose of skill in the art.

When in the nominal position, clamping device 136 is disposed adjacentthe lower surface of upper wall 122 between end walls 124 and 126. Theend walls are spaced to align the clamping device and orifice 140end-to-end with the upper wall and orifice 132. Each end wall isinwardly tapered adjacent the upper wall so as not to obstruct themovement of the clamping device. Upper wall 122 includes a pair ofalignment structures 142 adapted to align the clamping device andorifice 140 side-to-side with the upper wall and orifice 132. Whenclamping device 136 is in the nominal position, orifice 140 is generallyaxially aligned with orifice 132 and orifice 130 to slidably receive thebrace member.

Clamping device 136 is held in the nominal position by a yieldablesupport element such as spring 144 that engages the clamping deviceadjacent a first end 146, as well as a releasable restraining mechanism148 that engages the clamping device adjacent a second end 150. Firstend wall 124 includes a recessed region adapted to hold a portion ofspring 144 and align the spring with the clamping device. Althoughspring 144 is depicted as a compression spring, it will be appreciatedthat spring 144 may be any type of spring or other mechanism adapted toyieldably hold first end 146 adjacent the lower surface of upper wall122.

Restraining mechanism 148 may take any of a variety of differentconfigurations adapted to releasably support second end 150 of theclamping device. In the exemplary embodiment, drive mechanism 138 (whichwill be discussed in more detail below) exerts a constant downward forceon the clamping device adjacent second end 150. Restraining mechanism148 is configured to support the clamping device against the forceexerted by the drive mechanism. Typically, though not necessarily, therestraining mechanism is generally aligned with the drive mechanism toreduce any bending stress to the clamping device.

Exemplary restraining mechanism 148 is selectively collapsible torelease the second end of the clamping device. The restraining mechanismincludes an elongate collapsible base 154 adapted to support an elongatebrace 156. In its uncollapsed state illustrated in FIGS. 17-19, a lowerend 158 of base 154 rests on the upper surface of lower wall 120. Thebase extends upward from the lower wall toward the clamping device. Alower end 160 of brace 156 rests on an upper end 162 of base 154. Thebrace extends upward from the base to support the clamping device. Whenthe base collapses, the brace is dislodged, thereby releasing theclamping device as shown in FIGS. 20-21.

When in the uncollapsed, upright position, one side of base 154 isdisposed against a buttress structure 164. One side of lower end 160 ofthe brace is also disposed against the buttress structure, while anupper end 166 of the brace is disposed against a shoulder structure 168on the clamping device. Shoulder structure 168 is configured to positionthe brace in upright alignment on top of the base. Base 154 and brace156 are clamped against the buttress structure by a stabilizer member170. The stabilizer member is held in clamping engagement with the baseand the brace by a fusible member 70 such as described above and in theincorporated references. Fusible member 70 extends from the stabilizermember, over a contact mount 72 to an anchor point 172. Contact mount 72is coupled to a firing subsystem (not shown) adapted to supplysufficient electrical current to melt the fusible member. In theexemplary embodiment, contact mount 72 is anchored to buttress structure164, which is constructed of an electrically non-conducting materialsuch as plastic, etc.

Lower end 158 of the base includes a beveled region 174 opposite thebuttress structure. As shown in FIG. 19, beveled region 174 extendsthrough more than half the thickness of the base. Lower end 160 of thebrace includes a beveled region 176 adjacent the buttress structure. Asa result, a portion of the downward pressure exerted on the clampingdevice by the drive mechanism is translated onto upper end 162 as apivoting force away from the buttress structure. The remainder of thedownward force is translated into a downward force on lower wall 128.The upper end of the base is prevented from pivoting outward so long asstabilizer structure 170 remains in place.

Those of skill in the art will appreciate that the particularconfiguration of restraining mechanism 148 described above provides amechanical advantage for supporting second end 150 of the clampingdevice under the downward force of the drive mechanism. The proportionof downward force translated into pivoting force on the base will varywith the depth of beveled regions 174 and 176. Beveled regions 174 and176 typically are configured so that much of the downward force appliedby the drive mechanism is translated into downward force on base 154rather than pivoting force. As a result, fusible member 70 is onlyrequired to support a portion of the force exerted by the drivemechanism. Indeed, several hundred pounds of downward force may betranslated into only 10-20 pounds of outward pivoting force onstabilizer structure 170. This allows the fusible member to have asmaller diameter, thereby requiring less energy to melt. Nevertheless,the outward pivoting force should be sufficient to ensure the basecollapses within 5-10 milliseconds, and preferably within 1-5milliseconds.

In any event, when stabilizer member 170 is released, the upper end ofbase 154 quickly pivots outward from the buttress structure andcollapses beneath the brace, as illustrated in FIGS. 19 and 20. Upperend 166 of the brace includes a beveled region 178 opposite shoulderstructure 168 to allow the lower end of the brace to freely pivotoutward from the buttress structure along with the base. Second end 150of the clamping device is thereby released to move downward under theurging of the drive mechanism.

While second end 150 of the clamping device is pushed downward by thedrive mechanism, first end 146 is pushed upward by spring 144. As aresult, clamping device 136 pivots about brace member 108 into thelocked position where the edges of orifice 140 bind against the sides ofthe brace member as shown in FIG. 20. The angle through which theclamping device must pivot before binding against the brace member willvary based at least partially on the size differential between orifice140 and brace member 108. It is believed that the binding forcegenerated by the clamping device against the brace member is increasedwhere the pivot angle between the nominal position and the lockedposition is relatively small. Therefore, orifice 140 typically is sizedto fit relatively closely around the brace member. For example, in anembodiment where brace member 108 takes the form of a rod having acircular cross-section with a diameter of approximately 0.375-inch, onesuitable diameter for orifice 140 would be approximately 0.376-inch.Alternatively, other diameters may also be used within the scope of theinvention. For clarity, the size difference between orifice 140 andbrace member 108 is shown substantially exaggerated in FIGS. 18, 20 and21.

As mentioned above, drive mechanism 138 is disposed between upper wall122 and second end 150 of the clamping device. The drive mechanism isconfigured to urge the second end and upper wall apart when the clampingdevice is released from restraining mechanism 148. Once clamping device136 pivots to the locked position, further downward movement of secondend 150 is prevented because the clamping device is locked against thebrace member. As a result, the additional drive force exerted by thedrive mechanism forces upper wall 122 and housing 118 upward relative tothe clamping device and brace member, as illustrated in FIG. 21. Sincethe housing is coupled to pivot arm 98, the pivot arm is forced upwardas well.

Drive mechanism 138 should be configured to overcome the downwardmomentum of the pivot arm as well as any transferred angular momentumcaused by stopping blade 40. In addition, the upward force exerted bythe drive mechanism on the housing should be substantially larger thanany downward force exerted by spring 144. Typically, the drive mechanismis configured to provide 100-500 pounds of upward force on the pivotarm. The length of upward travel of the pivot arm will depend on thelength of translation, or ‘throw,’ of the drive mechanism as well as thedistance second end 150 pivots downward before locking against the bracemember.

In the exemplary embodiment, drive mechanism 138 includes a plurality ofBelleville springs 180 stacked in series. The number of springs in theseries is selected to provide a desired throw. Optionally, each springin the series may alternatively be plural springs stacked in parallel toprovide a desired amount of driving force. Springs 180 are disposed in arecessed region 182 of upper wall 122. The recessed region is sized tomaintain the springs in general axial alignment. Additionally, clampingdevice 136 includes a spindle structure 183, adapted to fit within thecentral bores of at least a portion of the springs to maintain alignmentbetween the springs. The spindle structure also serves to maintainalignment between the springs and the clamping device. It will beappreciated by those of skill in the art that drive mechanism 138 mayalternatively take any of a variety of other configurations adapted tolock the clamping device against the brace member and force the pivotarm upward. For example, the drive mechanism may include a coilcompression spring, explosive device, etc.

In any event, once the retraction assembly has been triggered, it may beuncoupled from the pivot arm and slid off the brace member. A new,untriggered retraction assembly may then be installed to place miter saw89 and safety system 18 back in operation. Alternatively, the triggeredretraction assembly may be reset using a new fusible member.

While one particular implementation of retraction assembly 110 has beendescribed, it will be appreciated that numerous alterations andmodifications are possible within the scope of the invention.Additionally, while the retraction assembly has been described in thecontext of retracting the pivot arm of a miter saw, it will beappreciated that the retraction assembly may also be adapted for use inother ways and on other machines.

Machines that include various components and features discussed abovemay be described as follows:

A cutting machine comprising a cutter; a brake adapted to stop thecutter, where the brake has an idle position and a braking position; andan actuation system adapted to selectively move the brake from the idleposition to the braking position, where at least a portion of theactuation system must be replaced after moving the brake from the idleposition to the braking position; wherein the actuation system includesan explosive device.

A cutting machine comprising a support structure; a cutting tool adaptedto cut a workpiece, where the cutting tool is supported by the supportstructure; a detection system adapted to detect a dangerous conditionbetween the cutting tool and a person; a reaction system adapted toperform a specified action upon detection of the dangerous condition; anexplosive to trigger the reaction system to perform the specified actionupon firing of the explosive; and a firing subsystem to fire theexplosive upon detection of the dangerous condition.

INDUSTRIAL APPLICABILITY

The present invention is applicable to power equipment, and specificallyto woodworking equipment such as table saws, miter saws, band saws,circular saws, jointers, etc. The present invention provides a safetysystem or reaction system wherein a cutting tool or other dangerous itemis retracted upon the occurrence of a specified event, such as whenaccidental contact between a user and a blade is detected. Retraction ofa cutting tool, for example, can minimize any injury from accidentalcontact with the cutting tool by reducing the amount of time the cuttingtool is in contact with a user or by moving the cutting tool to aposition where the user cannot contact it. A retraction system may beused in combination with other safety features to maximize theperformance of an overall safety system. For example, a retractionsystem may be used with a system that quickly stops a cutting tool sothat the cutting tool simultaneously stops and moves away from a user. Afusible member or explosive may be used to trigger the reaction systemto perform the specified action. A firing subsystem may be used to fusethe fusible member or fire the explosive upon detection of the dangerouscondition.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A method of operating a woodworking machine, where the woodworkingmachine has a work surface defining a cutting region and a cutting toolthat extends at least partially into the cutting region, the methodcomprising: moving the cutting tool; detecting a dangerous conditionbetween a person and the cutting tool; and retracting the cutting toolbelow the work surface within approximately 14 milliseconds after thedangerous condition is detected by the detection system.
 2. The methodof claim 1, where the dangerous condition is contact between a personand the cutting tool.
 3. The method of claim 1, where the dangerouscondition is proximity of a person to the cutting tool.
 4. The method ofclaim 1, further comprising firing an explosive to cause the retractingof the cutting tool.
 5. The method of claim 1, further comprisingstopping the retracting of the cutting tool.
 6. The method of claim 1,further comprising providing a stop to limit the retracting of thecutting tool.
 7. A woodworking machine comprising: a work surfacedefining a cutting region; a cutting tool positioned to extend at leastpartially into the cutting region; a detection system adapted to detecta dangerous condition between a person and the cutting tool; and areaction system associated with the detection system and the cuttingtool, where the reaction system is configured to retract the cuttingtool below the work surface within approximately 14 milliseconds afterthe dangerous condition is detected by the detection system.
 8. Thewoodworking machine of claim 7 where the dangerous condition is contactbetween a person and the cutting tool.
 9. The woodworking machine ofclaim 7 where the dangerous condition is proximity of a person to thecutting tool.
 10. The woodworking machine of claim 7 further comprisinga stop to limit the retraction of the cutting tool.
 11. The woodworkingmachine of claim 10 where the stop includes an impact-absorbingmaterial.
 12. The woodworking machine of claim 7, where the reactionsystem includes an explosive.